This invention relates to an open-end friction spinning machine having a plurality of spinning units. Each spinning unit has two rollers that are arranged next to one another, are drivable in the same rotational direction and form a wedge-shaped gap used for the formation of yarn. A suction device connected to a vacuum supply system is assigned to the wedge-shaped gap and is used for holding the forming yarn in the wedge-shaped gap.
A device for open-end friction spinning having a single spinning unit is disclosed in EP-OS No. 34 427. A wedge-shaped gap used for the formation of yarn is formed by two rollers that are arranged next to one another and are drivable in the same rotational direction. One of the two rollers has a perforated shell surface and a suction insert arranged inside. The suction insert, with the suction slot, is aimed at the area of the wedge-shaped gap. The suction insert is connected to a vacuum supply system. In the case of a yarn breakage, the feeding of the fiber material to be spun is interrupted by a yarn guard, while all other drives and devices continue to run. In the interior of the suction insert of the perforated roller, a device is arranged by means of which the suction slot can be closed progressively. By means of this device, a yarn end can be sucked into the area of the wedge-shaped gap prior to a piecing process. Subsequently, for the actual piecing, the suction slot is opened again and the fiber feeding means are turned on. A production machine would have to be composed of a plurality of such systems.
One object of the present invention is to provide an open-end friction spinning machine having a plurality of spinning units in such a way that a construction is obtained that is simple.
Another object of the present invention is the provision of an open-end friction spinning machine wherein the individual spinning units may be operated individually, without impairment of the operation of the adjacent spinning units.
These and other objects of the present invention are achieved by a construction wherein the suction devices of the spinning units are connected to a joint vacuum supply system by means of connecting lines, and wherein the spinning units are equipped with means for the blocking of the connecting line arranged in the connecting line between the suction devices and the vacuum supply system. The blocking means for the blocking of the connecting line are activiated by means for monitoring of spun yarn in the case of yarn breakage in especially preferred embodiments of the invention. Other means that are activated by the means for the monitoring in the case of yarn breakage are provided for at least approximately maintaining constant the air throughput in the vacuum supply system.
In order to ensure a construction of an open-end friction spinning machine that is as simple as possible, a joint vacuum supply system is provided to which the suction devices of the individual spinning units are connected. In order to avoid that in the case of a yarn breakage fiber residues that may have remained in the wedge-shaped gap and are no longer withdrawn are twisted together to form a hard yarn bead which may cause damage, it is provided that at the time of a yarn breakage, the suction device of the concerned spinning unit is also turned off. The fiber residues that may still be in the wedge-shaped gap will then no longer be sucked into the wedge-shaped gap.
The effect of the suction devices of the individual spinning units has an important influence on the spinning conditions and thus also on the produced yarn. Accordingly, it is provided at the same time that when a yarn breakage occurs at several spinning units and the corresponding suction devices are therefore, blocked, there will be no increased suction effect due to the increased air throughput at the other spinning units. Therefore, the spinning conditions at these spinning units remain unchanged. This is especially advantageous when an open-end friction spinning machine is started and the individual spinning units are started one after the other. If it were not provided that the air throughput in the vacuum supply system, and thus also in the spinning units already started, is maintained constant, the effects of the suction devices of the already started suction units would vary, resulting in considerable variation in the spun yarn qualities.
In one development of the invention, it is provided that each spinning unit is equipped with an auxiliary suction device. The means for the monitoring during a yarn breakage connects the auxiliary suction device with the vacuum supply system instead of the suction device. This auxiliary suction device is designed for at least approximately the same air throughput as the suction devices. This ensures that when the suction devices of several spinning units are blocked, because of yarn breakage or in the case of a starting of the spinning machine, the same air throughput is ensured at the individual spinning units and thus in the whole vacuum supply system. The overall air balance is thus kept constant so that the air balance at each individual spinning unit is also unchanged.
In a preferred embodiment of the invention, it is provided that each spinning unit is equipped with at least one air inlet opening that is used as the auxiliary suction device and can be connected with the vacuum supply system instead of the suction device. By means of a corresponding dimensioning of the cross section, this type of air inlet opening in a simple way can be adjusted such that through it, the same amount of air is taken in as by means of the suction device with the same supplied vacuum.
In a further development of the invention, it is provided that the air inlet opening connect to a duct whose mouth is aimed at the wedge-shaped gap. Thus the auxiliary suction device performs an additional function, i.e. a cleaning function by means of which the area of the wedge-shaped gap is subjected to suction in the case of a yarn breakage. It is thus possible to remove by suction the residual fibers remaining in the area of the wedge-shaped gap in the case of a yarn breakage which are no longer held in the wedge-shaped gap by the effect of the suction device.
In a further development of the invention, it is provided that the air inlet opening can be connected with a duct, the mouth of which is located in the area of a feeding and opening device. Thus, by means of the auxiliary suction device, another function can be carried out, namely the function of the cleaning of the feeding and opening device. In order to intensify the cleaning of the wedge-shaped gap as well as of the feeding and opening device, it may be provided as a development of the invention that compressed-air nozzles are in each case assigned to the mouth of the corresponding ducts which are opened at the time of a yarn breakage so that the cleaning will then be assisted by the discharged compressed air.
In a further development of the invention, it is provided that the mouth of the duct, as an extension of the wedge-shaped gap, is preferably arranged on the side that faces away from a yarn withdrawal device. Thus, this auxiliary suction device can be assigned another function during the start spinning process because then, by means of this auxiliary suction device, the yarn end that is to be returned to the area of the wedge-shaped gap for the piecing process is taken in by suction . In order to be able to continue to utilize the auxiliary spinning device for the piecing process, it is provided in a further development of the invention that the means for the blocking of the suction device and the means for the connecting of the auxiliary suction device connected at the duct leading out in the proximity of the wedge-shaped gap can be switched to an intermediate position in which the suction device and the auxiliary suction device are connected to the vacuum generating system. Since this operating condition occurs in each case only at one spinning unit, the overall air balance is not disturbed significantly, so that an increased intake by suction is permissible for a short time.
In a further development of the invention, a sliding valve is provided as the means for the blocking and connecting of the suction device and the auxiliary suction device from and with the vacuum supply system, said slide valve being operable by means of an electromagnet controlled by a yarn guard. This results in a simple and effective construction. In an advantageous development, it is provided in this case that the electromagnet is arranged in such a way that it locks the slide that is stressed by means of a spring in the operating position. The electromagnet then does not have to act continuously against the spring but must only be excited in the case of a yarn breakage for the unlocking of the slide. It will then also be advantageous that an actuating element is assigned to the slide which in each case projects out of the spinning unit. By means of this actuating element, the slide can then be actuated during a piecing process by a servicing apparatus that can be applied to the corresponding spinning unit and controls the piecing process.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.